Which of the following is necessary to increase the rate of a reaction? a. a decrease in the frequency of collisions b. an increase in the frequency of collisions c. a decrease in the frequency of successful collisions d. an increase in the frequency of successful collisions

Rate of the reaction is the decrease in concentration of the reactant or increase in the concentration of products per unit time.

Factors like concentration (pressure) of the reactant, nature of reactant, catalyst, surface area of the reactant, affect the reaction rate. Greater the concentration of the reactant, higher will be the number of effective collisions between the reactant molecules per unit time. So, the rate of reaction would increase with increase in frequency of successful collisions due to the increase in concentration of the reactants.

So, the correct answer is D. an increase in the frequency of successful collisions

i think it is true since you can test the answer and can use observations to complete it.

answer: semi-infinite solid initially at a uniform temperature of 400 ◦c is cooled at its surface by convection. the cooling fluid at a constant temperature of 200 ◦c has a convective coefficient (ha) of 250 w/m2.k. the physical properties of the solid: k = 20 w/m.k and α = 4 * 10-5  m2/s. using δx = 0.04 m and δt = 10 s. write the finite difference equations describing the transient heat transfer of the first five δx and the temperature profile after 30 s.